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KOLOS
KOLOS
KOLOS
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KOLOS interlocking concrete armour block
3D view of KOLOS
KOLOS units being cast
KOLOS units at Krishnapatnam Port Breakwater

KOLOS is a wave-dissipating concrete block intended to protect coastal structures like seawalls and breakwaters from the ocean waves. These blocks were developed in India by Navayuga Engineering Company and were first adopted for the breakwaters of the Krishnapatnam Port[1] along the East coast of India.

Design

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KOLOS has been conceptualized by incorporating structural improvements to existing armour units, Dolos. The common failure modes for Dolos were found to be either at the shank due to torsion and at the fluke by bending-induced shear.[2] The higher structural stresses are caused largely due to the longer lever arm. The elongated shank length of the Dolos was shrunken by 21.4% in KOLOS. The material thus saved compensates for thickening the legs of KOLOS.

KOLOS is characterized by a central shorter concrete member and two outer elongate concrete members connected on opposites sides of the central member. The outer members have parallel longitudinal axes extending normal to the longitudinal axis of the central member. These members have an octagonal cross-section and are further configured such that their cross-sectional area decreases from its intermediate portion towards opposite ends thereof.[3]

Casting and transportation

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KOLOS are fabricated using plain cement concrete. To fabricate KOLOS, three piece steel moulds are used which facilitate easy de-moulding. De-moulding is usually carried out after 24 hours of concrete casting.

A single KOLOS unit can weigh from 1.5 tons to 12 tons.

Lifting the units is done after three days of curing. The units are transferred from the casting bed to the stacking yard. Lifting of the units is done by slinging and hoisting with a crane. Trucks are used for the short haul to the breakwater.

Placement

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KOLOS are randomly placed on rubble mound breakwaters in two layers. Like most of the concrete armour units, the hydraulic stability of KOLOS is dictated by its self weight and interlocking with surrounding units. KOLOS is found to have almost the same level of porosity as Dolos with a layer coefficient of 1. The random placement of the units facilitates increased rate of placement and less dependence on complex placement techniques. A damage level of 0.5% is allowable in the design of KOLOS armour layer without inflicting damage to the underlayers of the breakwater.[3]

See also

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References

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Revisions and contributorsEdit on WikipediaRead on Wikipedia

KOLOS

View on Grokipedia
from Grokipedia
KOLOS is a patented armor unit developed by Navayuga Engineering Company Ltd. in , serving as a modified version of the block to enhance stability and wave energy dissipation in coastal structures such as breakwaters and seawalls. Designed with a unique interlocking geometry, it achieves one of the highest stability coefficients (K_D = 32) among similar units, making it particularly effective in high-energy wave environments and cyclone-prone areas. The development of KOLOS addressed limitations in earlier armor units like , which were prone to breakage under extreme conditions, by incorporating structural modifications that improve hydraulic performance without requiring . Hydraulic model tests have demonstrated its resistance to wave forces, with low wave transmission coefficients and overtopping volumes, ensuring greater tranquility in protected harbor areas. These attributes allow for more economical construction on challenging substrates, such as soft marine clay up to 18 meters deep. KOLOS has been successfully deployed in major Indian port projects, including the breakwaters at on the east coast, Astaranga Port on the coast, and , where it has proven resilient against littoral drift and severe wave climates. has focused on random wave interactions and long-term durability to support sustainable coastal infrastructure.

Background and Development

Origins and Invention

The concrete armor block was developed by Navayuga Engineering Company Limited (NECL) in the mid-2000s as an innovative solution to enhance coastal protection in , building on existing concrete armor units to better withstand high-energy wave conditions. This development addressed key challenges observed in traditional designs during Indian coastal projects, including structural failures due to breakage and excessive wave overtopping that compromised breakwater integrity. NECL's motivation stemmed from the need for a more robust, unit capable of dissipating wave energy effectively while minimizing stress concentrations, particularly in the dynamic marine environments along the east coast. The invention process involved conceptualization and refinement by a team of engineers at NECL, resulting in KOLOS as a modified iteration of predecessor units like the , with optimized geometry to improve stability and hydrodynamic performance. Patented in , KOLOS holds the distinction of being the first armor block to receive such protection in the country, underscoring its novelty in local practices. While specific lead inventors are not publicly detailed beyond the NECL engineering team, collaborative research contributions from experts such as P.V. Chandramohan, affiliated with NECL, played a pivotal role in its design evolution. Initial validation occurred through extensive hydraulic model testing, which demonstrated KOLOS's superior viability by achieving a stability coefficient (K_D) of 32—the highest recorded for any armor unit at the time—confirming its effectiveness in resisting wave attack and interlocking under irregular sea states. These tests, focused on hydrodynamic aspects like wave transmission and reflection, were instrumental in proving the block's potential for real-world deployment, paving the way for its inaugural use in the breakwaters.

Relation to Predecessor Designs

KOLOS represents a direct evolution from the , a pioneering armor unit developed in the , by addressing key structural vulnerabilities exposed in field applications. Specifically, the shank length in KOLOS is reduced by 50% compared to the , which helps mitigate breakage risks during severe storms where elongated shanks experienced high torsional stresses and fluke bending. This modification redistributes material to thicken the legs, enhancing overall durability while maintaining a comparable for similar deployment densities. Building on earlier designs like Tetrapods and Accropodes, KOLOS integrates advanced features to achieve greater stability under high-energy wave conditions. Unlike the Tetrapod's four-legged radial symmetry, which provided moderate interlocking but limited , or the Accropode's optimized single-layer placement for steep slopes, KOLOS emphasizes multi-point contacts that improve resistance to wave uplift and rocking without requiring precise orientation. These enhancements stem from empirical observations of breakwater performance, particularly the 1990s failures in Indian coastal projects where slender units like suffered extensive damage from cyclonic waves, prompting a focus on robust hydraulic response. The design philosophy of KOLOS marks a shift toward armor units with increased and hydraulic , allowing better wave absorption through void spaces that reduce reflection coefficients. A key differentiator is the adoption of octagonal cross-sections in its elongate members, which facilitate superior dissipation via streamlined flow paths, while preserving the core interlocking principle that ensures collective stability in random placement. This conceptual refinement, validated through physical modeling, positions KOLOS as a more resilient option for deep-water breakwaters.

Design Characteristics

Structural Components

The KOLOS armor unit is designed with a core structure comprising a central shorter stabilizing member flanked by two outer elongate members, which connect on opposite sides of the central member to form a Y-shaped configuration that promotes hydraulic stability and wave energy dissipation. This geometry allows the unit to interlock effectively with adjacent blocks while maintaining comparable to its predecessor, the . The legs of the KOLOS are thickened relative to the design to enhance impact resistance during wave loading, with the additional derived from a proportional reduction in shank length to 78.6% of the Dolos equivalent, optimizing material use without compromising overall stability. The outer elongate members feature octagonal cross-sections that taper from the intermediate portion toward the ends, reducing the surface area exposed to hydrodynamic forces and thereby minimizing uplift and drag effects. Interlocking is achieved through curved flukes at the ends of the elongate members, which enable mutual gripping between units even in random placement, ensuring a robust armor layer that resists displacement under severe wave conditions. This self-stabilizing feature supports deployment in single- or double-layer configurations on rubble-mound breakwaters.

Materials and Specifications

KOLOS units are fabricated from high-strength plain concrete (PCC) incorporating standard aggregates such as and sand, with no reinforcement to mitigate risks in saline environments. This composition ensures durability and abrasion resistance under wave impact, aligning with guidelines for armor units in coastal structures. The units are scalable in size and weight to suit project scales. is optimized for , contributing to a layer of 1.0 that supports efficient single-layer placement. Stability is designed per Van der Meer criteria, permitting an allowable level of 0.5, defined as rocking without displacement or breakage of units. KOLOS achieves one of the highest stability coefficients (K_D) among similar units at 32. Customization of KOLOS units accommodates site-specific conditions, such as increasing mass and dimensions for higher wave heights on exposed coasts, while maintaining the core PCC formulation to preserve hydrodynamic performance.

Manufacturing Process

Casting Techniques

The casting of KOLOS blocks begins with the use of multi-piece molds designed for precise shaping of the complex geometry of the modified , which enables efficient production and straightforward demolding without damaging the intricate features. These molds are constructed from durable to withstand repeated use in high-volume , ensuring consistency in block dimensions and surface finish. The of the multi-piece configuration allows for the accommodation of the block's unique protrusions and voids, facilitating the creation of stable, wave-dissipating units. Once the molds are prepared and secured, the concrete mix—typically a high-strength grade suitable for marine environments—is poured into the molds in a controlled manner to fill all cavities uniformly. To eliminate air voids and achieve dense compaction, the filled molds are subjected to using industrial vibrators, followed by leveling with a or to ensure a smooth top surface. This process is critical for enhancing the structural integrity of the blocks by promoting proper consolidation of the aggregate and paste. Demolding occurs after an initial setting period, at which point the has achieved sufficient strength to maintain its shape while allowing safe removal from the molds without cracking or deformation. The multi-piece mold design simplifies this step, as each section can be sequentially detached, minimizing stress on the fresh and preserving the design's precision. To support large-scale deployment in coastal projects, KOLOS blocks are produced via batch in dedicated factories located near sites, reducing transportation costs and logistical challenges. These facilities enable timely supply for breakwater and installations while maintaining quality through standardized processes.

Quality Control and Curing

The curing protocol for KOLOS blocks begins immediately after demolding and involves moist curing in shaded areas, followed by air drying to reach full strength. This method promotes uniform hydration of the while minimizing thermal stresses and surface cracking, particularly in tropical climates. inspections are conducted post-curing to verify structural integrity and compliance with specifications. Visual examinations detect surface cracks, honeycombs, or segregation, while dimensional accuracy is measured using or laser tools. Compressive strength testing follows IS 516 procedures, where samples from the same batch are loaded to failure in a to confirm the blocks meet the minimum strength requirements. Defects identified during are handled systematically to maintain batch . Blocks exhibiting significant defects are to prevent deployment risks. Minor imperfections may be repaired, followed by re-testing before acceptance. Final certification verifies adherence to Indian Standards, particularly IS 456 for and . Additional project-specific hydraulic tests ensure the units satisfy performance criteria for coastal protection applications. Certified blocks receive documentation including test reports and markings.

Installation and Deployment

Transportation Logistics

KOLOS blocks are lifted from the casting yard using overhead cranes or heavy-duty forklifts after sufficient curing to allow handling. The blocks are then secured on flatbed trucks to prevent damage during movement. For projects in , transportation typically involves short-haul distances to coastal ports. For heavier units, specialized trailers may be used. are managed to ensure safety, including monitoring weather conditions.

Placement Procedures

As a modified version of the unit, KOLOS is placed in a double-layer random system on rubble mound breakwaters to ensure hydraulic stability and promote for wave . Heavy-lift cranes with slings or mechanical grabs are used for placing the blocks. Placement typically starts at the seaward and proceeds upward along the slope, with monitoring to verify interlock. For high-wave exposure sites, the armor layer is designed according to site-specific stability requirements, with slopes often ranging from 1:1.5 to 1:2.

Applications and Performance

Initial Implementation

The debut project for KOLOS blocks took place at in , , where they were deployed as part of the harbor expansion breakwaters completed in the mid-2000s. Developed by Navayuga Engineering Company Limited as a modified unit with enhanced stability, the blocks were selected for their properties to armor the rubble mound structures against high-energy waves in the . The implementation created a sheltered basin for operations. Construction faced challenges from season delays in unit placement, which were addressed through a phased installation approach that prioritized dry-weather periods for offshore positioning. Placement procedures emphasized careful handling to ensure interlock, with units positioned using cranes from barges. Post-implementation results demonstrated the blocks' effectiveness, with model studies showing wave overtopping reductions of 7% to 45% compared to rubble mound designs without armor. Additionally, no unit breakage occurred despite exposure to the region's intense storm conditions, validating the design's durability in real-world coastal environments. KOLOS units have also been deployed at other Indian ports, including Astaranga Port on the coast and , demonstrating resilience against littoral drift and severe wave climates.

Hydraulic Stability and Testing

Hydraulic stability of KOLOS armor units was rigorously evaluated through physical model tests conducted at the Central Water and Power Research Station (CWPRS) in , . These tests confirmed the units' robust performance under dynamic wave forces without significant displacement or breakage, highlighting their suitability for rubble-mound breakwaters in high-energy environments. Field monitoring at the breakwater has underscored the units' resilience during cyclonic events, with minimal rocking or extraction observed. Key performance metrics of KOLOS include its high , comparable to that of units at approximately 50%, which facilitates effective wave energy dissipation through void spaces while maintaining structural integrity. The modified design enhances resistance to rocking and extraction compared to traditional , reducing the risk of armor layer failure under prolonged wave attack. Recommendations emphasize periodic inspections every 5-10 years to monitor for potential wear, particularly in high-sediment zones, to ensure sustained performance.
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